Scintillation properties of CsSrX3:Eu (CsSr1−yEuyX3, X = Cl,Br; 0 ≤ y ≤ 0.05) single crystals grown by the Bridgman method

The single crystals of CsSr_1−yEu_yCl₃ and CsSr_1−yEu_yBr₃ (0 ≤ y ≤ 0.05) grown by the Bridgman method have been investigated for their scintillation properties. The radioluminescence spectra of the crystals demonstrated a narrow band at 400–500 nm which peak position shifts continuously toward larger wavelength as the Eu²⁺ concentration increases. The scintillation light yield achieves maximal value of 33,400 ± 1700 photons per MeV with energy resolution of 11.5% at CsSr_0.95Eu_0.05Cl₃ and 31,300 ± 1600 photons per MeV with energy resolution of 9% at CsSr_0.95Eu_0.05Br₃. The decay times at room temperature are 2.7 ± 0.2 μs and 2.5 ± 0.2 μs, respectively.     

Comparative study of nondoped and Eu-doped SrI2 scintillator

Optical and scintillation properties of nondoped and Eu 3% doped SrI₂ crystals grown by the Vertical Bridgman method were investigated. Eu-doped crystal showed an intense single band emission at 430 nm due to the Eu²⁺ 5d-4f transitions in both photoluminescence and scintillation while the nondoped crystal had a complex spectral shape. The latter emission consists of mainly four bands: 360 nm, 540 nm, 410 nm and 430 nm. The origins of 360 nm and 540 nm were self-trapped exciton and unexpected impurity, respectively. The origins of 410 and 430 nm lines were ascribed to F center in different I sites. Under ¹³⁷Cs γ-ray irradiations, both crystals showed a clear photoabsorption peak. The scintillation light yields of the nondoped and Eu-doped SrI₂ resulted 33,000 ph/MeV and 82,000 ph/MeV, respectively. The energy resolution at 662 keV of Eu-doped was 4% while that of the non-doped SrI₂ was 8%.     

Effects of gamma-irradiation on Al2O3 crystals grown under reducing atmosphere

Gamma-ray irradiation-induced color centers in Al₂O₃ crystals grown by temperature gradient techniques (TGT) under a strongly reducing atmosphere were studied. The transition F⁺ → F takes place during the irradiation process. Glow discharge mass spectroscopy (GDMS) and annealing treatments show that Fe³⁺ impurity ions are present in the crystals. A composite (F⁺-Fe³⁺) defect was presented to explain the origin of the 255 nm band absorption in the TGT-Al₂O₃ crystals.     

Crystal growth and scintillation characteristics of the Nd doped LiLuF4 single crystals

Sixty millimeter diameter single crystal of Nd³⁺ doped LiLuF₄ was successfully grown by the Czochralski technique. No remarkable absorption due to unfavorable impurities was observed from optical absorption measurements in the vacuum ultra-violet spectral region. The high crystallinity and homogeneous luminescence characteristics were found from X-ray rocking curve and cathode-ray luminescence respectively. X-ray excited luminescence spectrum was measured and the significant 4f²5d-4f³ luminescence at 182 nm was observed in the grown crystal. The pulse height spectrum was taken upon γ-ray irradiation. As a result, the grown crystals demonstrated sufficient response to the γ-ray showing the light yield of 420 ± 30 photons/MeV. The decay curve under α-ray irradiation was also investigated and described by two component decay kinetics which consists of the decay constants of 34 and 450 ns.     

Optical investigations on Tb3+ doped l-Histidine hydrochloride mono hydrate single crystals grown by low temperature solution techniques

The potential nonlinear optical material of Terbium (Tb³⁺) ion doped l-Histidine hydrochloride monohydrate (LHHC) single crystals were successfully grown. Tb³⁺:LHHC crystals of 7 mm × 5 mm × 3 mm and 59 mm length and 15 mm diameter have been grown by the slow solvent evaporation and Sankaranarayanan-Ramasamy (SR) techniques respectively. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystalline structure and morphology. High resolution X-ray diffraction (HRXRD) studies revealed that the SR grown sample shows relatively good crystalline nature with 9″ full-width at half-maximum (FWHM) for the diffraction curve. Functional groups were identified by Fourier transform infra-red spectroscopy (FTIR). The optical transparency and band gaps of grown crystals were measured by UV–Vis spectroscopy. Thermogravimetric and differential thermal analysis (TG/DTA) studies reveal that the crystal was thermally stable up to 155 °C in SR grown crystal. Surface morphology of the growth plane was observed using scanning electron microscopy (SEM). The incorporation of Tb ion was estimated by EDAX. The frequency-dependent dielectric properties of the crystals were carried out for different temperatures. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the SR method grown crystal. Second harmonic generation efficiency of SEST and SR grown crystals are 3.2 and 3.5 times greater than that of pure KDP. The Photoluminescence (PL) studies of Tb³⁺ ions result from the radiative intra-configurational f-f transitions that occur from the ⁵D₄ excited state to the ⁷F_j (j = 6, 5, 4, 3) ground states. The decay curve of the ⁵D₄ level of emission was observed with a long life time of 319.2041 μs for the SR grown Tb³⁺:LHHC crystal.     

Concentration effect of Nd ion on the spectroscopic properties of Er/Nd co-doped LiYF4 single crystal

High quality Er³⁺/Nd³⁺:LiYF₄ single crystals were grown by a Bridgman method. Their spectroscopic properties were studied to understand the Nd³⁺ concentration effect upon excitation of an 800 nm laser diode. The intensest 2.7 μm emission was observed in the LiYF₄ crystal codoped with 0.99 mol% Er³⁺ and 0.62 mol% Nd³⁺. Meanwhile, the emission intensity for the green up-conversion and 1.5 μm downconversion of Er³⁺ decreased with increasing of the Nd³⁺ concentration. The modified Inokuti–Hirayama model was used to analyze the decay curves of the 1.06 (Nd³⁺) and 1.5 (Er³⁺) μm emissions. The results indicated that the energy transfer process (Er³⁺:⁴I_13/2 + Nd³⁺:⁴I_9/2 → Er³⁺:⁴I_15/2 + Nd³⁺:⁴I_15/2) is mainly due to the electric dipole–dipole interaction. The energy transfer efficiencies between Nd³⁺ and Er³⁺ ions were calculated. All results suggested that the Er³⁺/Nd³⁺:LiYF₄ single crystals may have potential applications in mid-infrared lasers.     

Piezospectroscopic study of mechanical stress in Al2O3:Cr under swift heavy ion irradiation

The spatial distribution of mechanical stresses in Al₂O₃:Cr single crystal irradiated with (1 ÷ 3) MeV/amu Kr, Xe and Bi ions has been studied by using laser confocal scanning microscopy technique. The stress level as a function of the ion penetration depth has been evaluated from depth-resolved photostimulated R-line luminescence spectra exploiting the piezospectroscopic method. As it was found, the stress field generated by swift heavy ion irradiation is composed of stresses with maximal magnitude comparable with the ultimate stress limit of ruby crystals. Experimental data are discussed in the framework of a model considering the Cr³⁺ atoms as individual piezosensors.     

On the observation of physical, chemical, optical and thermal changes induced by 50 MeV silicon ion in benzimidazole single crystals

The 50 MeV Si ion irradiation-induced modifications on structural, chemical, optical and thermal properties of Vertical Bridgman grown benzimidazole (BMZ) crystals have been studied. The FTIR studies have been used to analyze the variation in various bonds that are associated with the functional groups in the native and the irradiated sample. X-ray diffraction studies reveal the compressive strains that are generated due to irradiation. The effect of irradiation on the conductivity of BMZ crystals has been studied. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The thermal analysis reveals that the melting point remains unaffected and the sample does not decompose as a result of irradiation.     

Effect of SHI irradiation on the morphology of SnO2 thin film prepared by reactive thermal evaporation

SnO₂ thin films prepared by reactive thermal evaporation on glass substrates were subjected to 120 MeV Ag⁹⁺ ion irradiation. The surface topography progression using the swift heavy ion irradiation was studied. It shows creation of unique surface morphologies and regular structures on the surface of the SnO₂ thin film at particular fluences. Field Emission Scanning electron microscopy (FE-SEM) and Atomic force microscopy (AFM) are used for investigating the effect of Ag ions at different fluences on the surface of SnO₂. The morphological changes suggest that ion assisted/induced diffusion process play a significant role in the evolution of nanostructures on SnO₂ surface. The roughness increases from 9.4 to 14.9 with fluence upto 1 × 10¹² ions/cm² and beyond this fluence, the roughness decreases. Ion-beam induced recrystallization at lower fluences and amorphization or disordering of crystals at higher fluences are understood based on the thermal spike model.     

Thermal and spectroscopic studies of as-grown l-arginine hydrochloride monohydrate crystals

Single crystals of l-arginine hydrochloride monohydrate (LAHCl) were successfully grown at ambient temperature (28.5°C) from its aqueous solution (pH=5.4) by slow evaporation as well as by slow cooling methods.The as-grown crystal is of dimensions 2.8×4.5×1.2 cm³. Studies on the structural, chemical and thermal properties of the crystal have been carried out on the basis of X-ray diffraction (XRD), infrared spectroscopy (IR), carbon, hydrogen, nitrogen (CHN) analysis, thermogravimetric (TG) analysis and differential thermal analysis (DTA) measurements. IR absorption bands indicate the mode of vibrations of different molecular groups present in LAHCl. TG-DTA analysis gives an idea about the thermal behaviour of LAHCl and ruled out the possibility of structural changes independent of mass changes.     

Optical studies on X and γ irradiated vacuum grown CsBrI:Eu2+ crystals

CsBr_0.9I_0.1:Eu²⁺ crystals were grown by Bridgman technique. Optical absorption spectrum of the unirradiated CsBr_0.9I_0.1:Eu²⁺ crystals show absorption bands at 270 nm and 340 nm. Irradiated CsBr_0.9I_0.1:Eu²⁺ shows single F band for F(Br⁻) and F(I⁻) centers at 730 nm. Conversion of Eu²⁺ to Eu³⁺ after irradiation is confirmed by optical absorption technique. Sharp and single Photoluminescence (PL) emission band is observed at 440 nm for CsBr_0.9I_0.1:Eu²⁺ crystals. Photostimulated Luminescence (PSL) emission band observed for CsBr_0.9I_0.1:Eu²⁺ crystals at 442 nm due to excitation at 730 nm shows that the F centers are photostimulable. PSL emission intensity increases linearly with irradiation dose up to 2.5 Krad.     

Synthesis,growth and characterization of π conjugated organic nonlinear optical chalcone derivative

A new potentially useful nonlinear optical organic material, 1-(5-chlorothiophen-2-yl)-3-(2,3-dimethoxyphenyl)prop-2-en-1-one, has been synthesized and grown as a high-quality single crystal by the slow evaporation technique. The grown crystals were characterized by FT-IR, NMR, thermal analysis, and UV–visible spectroscopy. The material is thermally stabile up to 111 °C. The mechanical property of the grown crystals was studied using Vickers microhardness tester and the load dependence hardness was observed. The third order nonlinear optical properties of the material such as real and imaginary part of χ⁽³⁾, nonlinear absorption coefficient and nonlinear refractive index were determined using nanosecond laser pulses at 532 nm wavelength by employing Z-scan technique. The nonlinear refractive index is found to be of the order of 10⁻¹¹ cm² W⁻¹. The magnitude of third order susceptibility is of the order of 10⁻¹³ esu. The observed increase in the third order nonlinearity in these molecules clearly indicates the electronic origin. The compounds exhibit good optical limiting at 532 nm. The best optical limiting behavior of this molecule is due to the substituted strong electron donor.     

Optical properties of swift ion beam irradiated CdTe thin films

This paper reports the effect of swift (80 MeV) oxygen (O⁺⁶) ion irradiation on the optical properties of CdTe thin films grown by conventional thermal evaporation on glass substrates. The films are found to be slightly Te-rich in composition and irradiation results no change in the elemental composition. The optical constants such as refractive index (n), absorption coefficient (α) and the optical band gap energy show significant variation in their values with increase in ion fluence. Upon irradiation the band gap energy decreased from a value of 1.53 eV to 1.46 eV whereas the refractive index (n) increased from 2.38 to 3.12 at λ = 850 nm. The photoluminescence spectrum shows high density of native defects whose density strongly depends on the ion fluence. Both analyses indicate considerable defect production after swift ion beam irradiation.     

Scintillation properties of Pr3+-doped lutetium and yttrium aluminum garnets: Comparison with Ce3+-doped ones

Scintillation properties of Pr³⁺-doped LuAG and YAG crystals were investigated and compared with those of Ce³⁺-doped ones. The highest L.Y.’s were observed with the longest shaping time 10 μs. They can reach up to ～16,000 ph/MeV or ～23,500 ph/MeV for LuAG:Pr and LuAG:Ce, respectively. Energy resolutions (FWHM) are a bit better with LuAG:Pr than those of LuAG:Ce, e.g. at 662 keV FWHM are around 6% and between 8–12%, respectively. There were observed no large changes in proportionality of Pr³⁺- or Ce³⁺-doped LuAG or YAG crystals but the best proportionality has YAP:Ce crystal. Pr³⁺- or Ce³⁺-doped LuAG crystals exhibit slow decay components in the time range 1.5–3.5 μs while those of YAG ones have shorter decay components between 0.3–1.7 μs.     

Microhardness,FTIR and transmission spectral studies of Mg2+ and Zn2+ doped nonlinear optical BTCC single crystals

Pure, Mg²⁺ and Zn²⁺ doped BTCC single crystals are grown from their aqueous solutions at 301 K. The grown crystals are characterized by single crystal XRD, FTIR and UV–Vis-NIR spectral studies. The preliminary investigations of the UV–Vis-NIR spectra on the doped samples suggest an increased percentage of transmission in comparison to pure BTCC crystals. The SHG efficiency of the metal doped BTCC crystals is found better than the pure ones. It is estimated from the microhardness studies that the mechanical strength of the BTCC crystals are improved due to the metallic (Mg²⁺ and Zn²⁺) substitutions.     

Synthesis,crystal growth,structural, spectral,thermal, mechanical,linear and nonlinear optical studies of organic single crystal 4-Iodo 4-nitrostilbene (IONS): A potential NLO material

An organic nonlinear optical material 4-Iodo 4-nitrostilbene (IONS) has been synthesized and good optical quality single crystal was grown from ethyl methyl ketone solvent by the solution growth technique. Single and powder X-ray diffraction analyses reveals that the grown crystal belongs to monoclinic crystal system with noncentrosymmetric space group ‘P2₁’ and it has good crystalline nature. Functional groups and molecular structure of the title compound were confirmed by FTIR and ¹H NMR respectively. The UV–Vis–NIR absorption study reveals no absorption in the visible region and the cut-off wavelength was found to be at 412.84 nm, TG/DTA, mass spectral analysis, photoluminescence and microhardness studies have been carried out for the grown crystals and results are discussed in detail. The second harmonic efficiency of the IONS was determined by Kurtz–Perry powder technique which reveals that the IONS crystal (3.1 V) has greater efficiency i.e., 143 times to that of KDP (21.7 mV).     

Optical and scintillation properties of SrI2:Yb2+

The luminescence and scintillation properties of SrI₂:0.5%Yb²⁺ have been investigated. SrI₂:Yb single crystals were grown by the vertical Bridgeman method from the melt. They showed a light yield of 38,400 ph/MeV and energy resolution of 12.5% for the 662 keV full absorption peak. Yb²⁺ photoluminescence intensity and decay time were studied between 78 and 600 K. Two emission bands centered at 418 and 446 nm were observed and ascribed to spin-allowed and spin-forbidden Yb²⁺ 5d-4f transitions, respectively. Their corresponding room-temperature decay time constants are 710 ns and 77 μs. Both, the emission intensities and the decay time constants vary with temperature. The obtained results were interpreted using a model of self-absorption of Yb²⁺ emission and a model of non-radiative relaxation of the electron from the low spin to the high spin 4f¹³5d Yb²⁺ excited states. The radiative lifetime of the low spin Yb²⁺ excited state was determined as 400 ns.     

GaN optical degradation during high energy Sn<Superscript>5+</Superscript> ion irradiation

GaN(0001) epilayers grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD) have been irradiated with 75 MeV Sn⁵⁺ ions at the fluences of 10¹¹, 10¹², and 10¹³ ions/cm². Structural and optical studies reveal that GaN epilayer withstands 75 MeV Sn⁵⁺ ion irradiations up to 10¹¹ ions/cm² ion fluences. High resolution X-ray diffraction results showed that the FWHM corresponding to (0002) plane increased from 227 to 279 arc-seconds after Sn-ions irradiation. Red shift was observed in the yellow luminescence (YL) emission by photoluminescence (PL), corresponds to the concentration of ion fluences. Donor-bound exciton (DBE) and free exciton (FE^A, FE^B and FE^C) emissions were observed for as-grown and irradiated GaN samples up to 10¹² ions/cm² at 2K PL measurements. Free excitons are dominated by low-temperature PL measurements for as-grown and irradiated GaN samples at 10¹¹ and 10¹² ion fluences. Atomic force microscopy images show the RMS roughness increases with increasing Sn-ion fluences by removing as-grown GaN surface defects.     

Titanium surface layers after irradiation with swift Kr and Xe ions

This paper presents the test results of the swift krypton (240 MeV) and xenon ion (130 MeV) irradiation influence on the titanium surface layer properties. These ions change the titanium surface topography in different ways. The irradiation contributes to the creation of a new phase in the surface layer. Radiation damage effects on the friction coefficient, wear, and microhardness of titanium after krypton and xenon ion irradiation were studied. Krypton irradiation does not influence the microhardness of the titanium. After xenon irradiation with a fluence of 1 × 10¹⁸ ion/m² the microhardness increases by 13%; further increases of the fluence gradually reduce the microhardness of the surface layer. Swift Kr and Xe ion irradiation does not influence the friction coefficient of the titanium surface.     

Ion irradiation induced amorphization of SnO2 nanoparticles embedded in SiO2

SnO₂ nanoparticles (NPs) of average diameter of ∼10.5 nm, synthesized in SiO₂ using Sn⁻ ions implantation combined with thermal annealing, were irradiated with 1.5 MeV Au²⁺ ions at room temperature. The NP structure was studied as a function of ion fluence by transmission electron microscopy and micro-Raman spectroscopy. Prior to ion irradiation, SnO₂ NPs have been found to exhibit the rutile crystal structure. Upon irradiation, amorphization in the nanocrystals has been seen to increase with increase in ion fluence. In particular, at a fluence of 1 × 10¹⁴ ions cm⁻² we argue for the presence of an amorphous SnO₂ phase. Beyond this fluence, the NPs have been found to dissolve in the matrix. The observed results are explained in the frame work of ion irradiation induced defects production in the NPs as well as in the NP/matrix interface.